In insects, RNAi (RNA interference) is a useful technique to suppress genes and a powerful tool for understanding the function and interaction of genes. Liu & Colleagues* used RNAi to dissect genes important in creating color patterns in the large milkweed bug, Oncopeltus fasciatus. They studied four genes, ebony, black, aaNAT, tan and yellow. Ebony and black are genes that suppress the production of melanin. As shown in the figure (left) knocking out the ebony gene or the black gene with injected RNAi created an unusual color pattern. Areas of the wings and body that are typically yellow or orange become black because of the increase in melanin production. RNAi analysis demonstrates that Oncopetus color pattern is the result of expressing or repressing genes that control the amount of melanin production.
The form and color of an insect are not only the result of the presence or absence of genes but also the timing a pattern of when and where they are expressed.
*Jin Liu, Thomas R. Lemonds, James H. Marden, Aleksandar Popadić. A Pathway Analysis of Melanin Patterning in a Hemimetabolous Insect. GENETICS May 1, 2016 vol. 203 no. 1 403-413;.